ARL improves technology for measuring obscurant transmissivity

Shown is a test of Army's bispectral grenade in August 2013. (Image provided by the U.S. Army Research, Development and Engineering Command)

Story Highlights

System developed that collects and analyzes battlefield obscurants' transmittance, resolving it spectrally in a range from the visible to the far infrared

Advanced grenade—the first ever designed for the Army—has immediate applications in countering thermal imagers, image intensifiers and thermal-guided threats

EETRANS is a novel idea SLAD developed using existing equipment and applying its own resources and expertise to solve the problem

During a recent event to study the performance of smoke and obscurants, researchers from the U.S. Army Research Laboratory's Survivability/Lethality Analysis Directorate set out to improve the process of measuring transmissivity—the fraction of electromagnetic radiation that passes through battlefield attenuators, such as are produced by smoke grenades.

In partnership with New Mexico State University and with the endorsement of DOD's Center for Countermeasures, they developed a system that collects and analyzes battlefield obscurants' transmittance, resolving it spectrally in a range from the visible to the far infrared.

"The new system, named EETRANS for 'Enhanced Electro-Optical Transmissometer System,' replaces one that was used for twenty or thirty years but lacks spectral dependence and is therefore obsolete," said Dr. Rudy Montoya, the project physicist. "The new method is much more precise and can provide analysis on obscurant transmission at a much higher fidelity. And, analysis can be done without additional field work because we can now use the measurements to produce a model of it."

Efforts to refurbish equipment, update spectrometer software and improve data-processing code have been ongoing since the system's use in tests of a bispectral-obscurant grenade. Designed to block visibility up to the far-IR range of the electromagnetic spectrum, this advanced grenade—the first ever designed for the Army—has immediate applications in countering thermal imagers, image intensifiers, and thermal-guided threats.

The initial testing to select the most efficient and best performing bispectral grenade fills was led by researchers from the Edgewood Chemical Biological Center and performed in their aerosol chamber at the Edgewood area of Aberdeen Proving Ground. The materials that had performed best in the initial testing were used as the fill in the new grenade configurations to assess their effectiveness against the visual backdrop of a special instrumented grid.

Joining SLAD and ECBC on the government side were the Aberdeen Test Center and the Communications Electronic Research, Development and Engineering Center. Also participating were NMSU and the Georgia Tech Research Institute.

"ECBC requested our expertise on this test to provide a new dimension of measurement to see through the cloud and further analyze the obscurants," said Alejandro Gongora, the EETRANS project lead. "Wideband systems have been used for decades, but they are not optimized. We developed this technique to do more precise measurements, which is why our team was contacted for this project."

Gongora said the characterization of battlefield obscurants will provide more meaningful data for the development of better weapon and countermeasure systems such as the bispectral grenade.

"To our knowledge, spectral-wide measurements—from the visible to the far-IR regions—taken during field tests had never been accomplished in the past, in spite of a long and expensive history," said Gongora. "This is the least expensive approach because the EETRANS data can be utilized by multiple weapons systems without additional testing for specific narrow bands of interest."

The EETRANS is a novel idea that SLAD developed using existing equipment and applying its own resources and expertise to solve the problem. "We have a lot of lessons learned from the initial tests," said Montoya. "With minimal investment, we have used existing equipment to build up this capability, so we'd like to continue its development. That's what the next step is—to make the instrumentation and process we use smoother for a more efficient product."

SLAD researchers are now refining the system. They plan to explore analysis of other spectral regions, such as ultraviolet and millimeter waves to characterize new battle byproducts. One goal is to integrate the EETRANS data products with battlefield obscurant modeling and simulation programs. Another is to assist with seeker sensor improvements for multiple military systems.

"The EETRANS is truly a survivability and lethality analysis tool," said Gongora. "This capability is in its early stages. We are looking forward to improving it and applying it for more customers."